The Research Of Expanded Graphite/Activated Carbon For Ship's Oily Water Treatment

Due to a stronger vibration and limited space in engine room on board ships,adsorption separation technique,which not only takes the advantages of simple structure,good separation effect and limited space,but also reduces the strength of the crew,is suitable for ship oil-water separation.Along with the emission regulations getting more and more stringent,it will have very realistic significance if we can develop the adsorbent with low cost and large adsorption capacity for ship's bilge water treatment.In this paper,a new composite adsorbent which is composed of expanded graphite and activated carbon was prepared by active agent H₃PO₄ through the sequence processes of impregnation,solidification,and activation.Researches undertaken are as follows:?1?Optimization of process parameters for the development of the activated carbon suitable for emulsified oil adsorption.Sucrose was selected as carbon source and H₃PO₄ was as activating agent.Single factor optimization method was employed to evaluate the influence of impregnation ratio of H₃PO₄ to sucrose,activation temperature and time as well as the increasing rate of temperature on adsorption capacity of emulsified oil on the sample.Results show that the largest emulsified oil adsorption capacity 57.6mg/g is obtained while a sample has the specific surface area 1095m²/g,and abundant meso-pores can be developed where the impregnation ratio,the heating temperature,the heating duration and the increasing rate of temperature are respectively set as 2.5,550?,2 h and 15?/min.?2?The influence of expansion process and molding process of the expandable graphite on the performance of the expanded graphite.The expanded graphite was firstly developed over a temperature range of 600-900? to evaluate expansion process parameters optimization.The monolith of the expanded graphite was formed by mechanical method was then undergone the mechanical-strength measurement.It shows that the as-prepared expanded graphite samples have the largest expansion volume where the temperature and duration for expansion were respectively about 900 ? and 25 s,and the mechanical strength of compressed expanded graphite block increases in the density.Results also reveal that,while the density is 0.03g/?cm^?3,the monolith can basically meet the mechanical strength required by filter material for bilge water processing.?3?Selection of the parameters for composite process and structure analysis of the composite adsorbent.The introduction of sucrose and H₃PO₄ can cause polycondensation reaction during the process of forming the monolith.The effect of sucrose mass fraction in sugar/H₃PO₄ and compressed expanded graphite block density on composite adsorbent radial dimensions changing was respectively evaluated for reducing the polycondensation reaction effect on the composite adsorbent size changing.It seems that the effect from dimensional changing of compressed expanded graphite block density was small,and when the sucrose mass fraction in sugar/H₃PO₄ mixed solution was up to 20% or more,the change of composite adsorbent in radial direction can be neglected.The SEM scan on the composite adsorbent shows that,due to the new "storage" space developed by introducing activated carbon,the performance of capturing the tiny droplets has greatly been enhanced.?4?Optimization of the dynamic adsorption process and mechanical strength test of the composite adsorbent.The influence from factors such as the density of the monolith,height of expanded graphite/activated carbon composite adsorbent and flow velocity on oily water separation was studied for the purpose of practical application of this technique on board ships It is found that selection of impregnation diameter 44 mm,height 20 mm and density 0.03g/?cm?³ and sucrose mass fraction of 20%in sucrose/H₃PO₄ is beneficial to the development of expanded graphite/activated carbon composite adsorbent.The composite adsorbent has the capacity of separating 10.35 L emulsified oil under the condition of initial setting velocity 2.6×10-4m/s with the treated effluent oil content less than 15 PPM.Moreover,due to introduction of activated carbon covering in the winding space,it makes the composite adsorbent compression resistance and crushing resistance significantly higher than that of the compressed expanded graphite monoliths.The composite adsorbent with monolith percent about 94.8% could basically satisfy the requirements of practical application for mechanical strength.